The combined effect of Ca and pH on fish and fisheries is considered for both laboratory and field studies. It can be seen that at concentrations less than 100 mu-eq/l, Ca can exert a significant influence on survival times of fish, and similarly in the field, the number of fishless lakes and the number of fish species found in lakes are less dependent on H('+) concentration at low concentrations of Ca than at high Ca levels. The limited historical field data available suggest that alongside any increase there may have been in surface water acidity, Ca concentrations have also increased, and the latter may have offset to some extent the deleterious biological effects of this increased acidity. Nevertheless, details of seasonal and spatial variations in these important water quality factors will need to be considered before a full understanding of the response to acidity of a fishery can be reached.

A detailed soil column leaching experiment was set up to investigate the changes in properties to a soil as a result of irrigation with an alkaline sanitary landfill leachate (pH 10.3). Chemistry of the soil was drastically altered as a consequence of the interaction. The soil was titrated from pH 5 to pH 10 and was changed from an exchangeable Mg dominated soil to an exchangeable Ca dominated soil. Magnesium was displaced by ion exchange reaction at acid pH, but at pH 10, 14.2 meq 100/g of Mg, i.e. up to three times the cation exchange capacity of Mg, was adsorbed in non-exchangeable forms at the immediate surface of the soil column by specific adsorption reactions. The leachate-treated soil was not stable on distilled water leaching. Structural breakdown led to clay dispersion and reduction in pore space, resulting in a 64 times reduction in hydraulic conductivity, 1.6 x 10('-4) to 2.5 x 10('-6) cm/s. The structural breakdown could be explained in term of the increase in Na adsorption ratio of the treated soil and the subsequent reduction in electrolyte concentration following the distilled water treatment.

Total airborne Hg as well as black particles (soot) were monitored in a number of clean air areas in Sweden. For some of the sampling sites, back trajectories for air movements at 850 mb were provided by the Norwegian Meteorological Institute. It is shown that the total Hg in air may be divided into two fractions. The most important one may be considered to be a background and is probably the result of re-emission of Hg by the ground and by natural water. The other fraction is highly dependent on wind direction in the same way as black particles. This fraction seems to be of anthropogenic origin.

Occurrence and distribution of organochlorine pesticides in the water of Lake Mariut, a brackish coastal Egyptian lake suffering from pollution, and their accumulation in the common fish Tilapia were studied. The major pesticides detected in the lake water were lindane, p, p'-DDE, o, p'-DDT, and p, p'-DDT. These compounds, except o, p'-DDT, were detected in the fish samples in exceedingly higher concentrations compared with those found in the lake water.

Numerous field and laboratory studies have shown measurable effects of soil acidification on soil processes and yet there is no indication to date that forest production is being affected even in heavily impacted areas. A discussion of possible reasons for this apparent contradiction is presented along with results of two computer simulations of possible responses to acid rain induced changes in (a) N availability and (b) soil organic matter decomposition rate. The first simulation shows a direct relationship between N availability and forest production. The second indicates the possibility for a more complex response with changes in total soil organic matter more than compensating for changes in decomposition rate and producing an inverse relationship between decomposition rate and N availability.

Crambe Crambe abyssinica and kenaf Hibiscus cannabinus were grown for 3 years on stripmine land in three replications of the four treatments: control (no soil amendment); added commercial fertiliser; and two levels of digested sewage sludge (42% solids at the rate of 112 and 224 metric tons ha-1). Favourable growth responses to sludge and commercial fertiliser were observed with both crops, although performance of crambe on the sludge-treated plots were adversely affected by weed competition. The yield of kenaf increased with sludge amendment of the soil. Concentrations of eight metals (Fe, An, Mn, Cu, Pb, Cr, Cd, and Hg) in crambe seed were unaffected by plot treatment, but kenaf stems appeared to accumulate higher metal concentrations with soil amendment by sewage sludge. Neither crambe seed nor kenaf stalks accumulated unusual quantities of these metals, and thus neither crop would be expected to remove significant quantities of metals from soils. Metal concentrations of both soil and sludge samples were determined to evaluate translocation of metals to both crops.